display a great variability in thickness. Their normal thickness of about 20 meters can increase in places up to 180 meters. These pronounced variations in thickness indicate a reefal origin of the marbles, most likely as bioherms. Calcsilicates The very fine-grained calcsilicates have a gneissose appearance. They originated from very potassium-rich marbles. They can take on the character of multicoloured (mainly light and greenish colours), banded hornfels. They contain the minerals diopside, tremolite, clinozoisite, basic plagioclase, microcline and microscopic biotite. At the type locality these calcsilicates form sandy calcschists. Rhyodacites The original rhyodacites (or rhyodacitic tuffs) have been metamorphosed to fine-grained leptynites. Stratigraphically they usually follow after the basal calcareous marbles, but occasionally they can be found somewhat higher above the calcareous marbles. Radiometric age dating on these rhyodacites yielded 581 million years supporting the Ediacarian age of the Canaveilles Group. Depositional environment Most likely the Canaveilles Group was deposited during the interval end-Neoproterozoic to lower Cambrian at the northern edge of Gondwana. The sediments are of marine origin and probably were left behind on the continental margin. Possible bioherms within the carbonaceous intercalations and the archeocyathid reefs in the Cadí Nappe point at shelf or shelf edge deposits with some incorporated reefal complexes. The rhyodacites probably were associated with an island arc, so it is possible that the Canaveilles Group was sedimented in a backarc position. This finds support in the group's close relationship with the Alcudian of central Iberia, a 15 kilometer! thick, strongly subsident Neoproterozoic sedimentary succession formed along a transform fault traversing the active northern margin of Gondwana. Metamorphism During the Variscan orogeny in the Pennsylvanian about 310 million years ago the sediments of the Canaveilles Group were metamorphosed under mesozonal conditions (amphibolite facies). The original shales transformed into mica schists of the cordierite, andalusite and sillimanite zone in the lower part of the section, higher up they only converted to greenschist facies phyllites of the biotite zone. The carbonaceous intercalations became marbles and calcsilicates. Close to the contact with the “transitional gneiss” first the andalusite isograd is reached, followed by the cordierite isograd. This indicates a magmatic origin of the gneisses formed from intrusive granitoids. Magmatism The sedimentary succession of the Canaveilles Group often is crosscut by dikes of two-mica granite and associated pegmatites. These dikes form part of the deep-seated Canigou granite. They intrude mainly the basal calcareous marbles and the dolomitic marbles, but